he oldest construction materi­
als were made out of clay.
Three principal forms of clay
are used: surface clay, fire
clay, and shale. During the
manufacturing process, clay is
crushed, grinded, mixed with water, formed
into a specified shape, and fired in the kiln.
The brick industry employs three principal
methods of forming brick: extruded, drypressed, and molded. Extruded and drypressed brick will have cores (holes) to
make the firing process more uniform.
Cores also save mass during the firing and
shipment of brick. The molded brick is
always solid but can have one depressed
bed side, called the “frog.”
The heart of a brick factory is the kiln,
where brick is fired under a temperature of
approximately 2000 degrees Fahrenheit
(1093 degrees Celsius). A contemporary
brick plant has a tunnel kiln with a nonstop
firing process. Older plants still operate
beehive kilns with a periodic firing process.
Ferrous oxides, such as iron, magne­
sium, and calcium, form a brick’s color dur­
ing the firing process. Brick will either have
a through-body color or a coated face such
as glazed, clay coat, and engobe.
In the United States, clay brick is man­
ufactured for different applications in
accordance with the American Society for
Testing and Materials (ASTM) specifica­
tions.
Facing brick is the most commonly used
product. The modular brick size is 3-5/8" x
2-1/4" x 7-5/8" (90 mm x 57 mm x 190
mm). Eleven other brick sizes are also in
use today.
Decorative brick shapes are available in
standard and custom sizes to form certain
architectural details such as water tables,
arches, copings, and corners. Clay is a pop­
ular material that artists use to create brick
sculptures and murals.
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In Mexico and some southern areas of
the United States, an adobe brick is made
by a sun-dried molded mix of clay, straw,
and water.
Normally, brick is packaged into steelstrapped cubes with openings for forklift
handling. The modular brick size has 500
brick units in a standard cube.
To find a good match for a brick replace­
ment, it is necessary to find exactly what
kind of brick is being used. Extruded and
dry-pressed brick will have perfectly cut
edges with an industrial look. Molded brick
will have a lip at the edge of a brick perime­
ter at the unfinished bed side. Molded brick
units normally have a colonial appearance.
The next step is to match the size of a
replacement brick. Try to stay within the
common brick sizes and no extra fee will be
charged for the replacement brick units. If
odd brick sizes are required, prepare to pay
extra dollars for them. A custom-size brick
production will require a minimum of 30 to
50,000 bricks in the run.
Most important is to match a color and
a texture of a replacement brick. Do not rely
on the manufacturer’s color catalog cuts for
the color representation. Even a good qual­
ity color printing will not provide actual
brick color appearance. Find the actual
brick samples and compare the samples
with the existing brick appearance right at
the building site. Make sure that the brick
sample is not older than 12 months.
The color of the mortar joints for
replaced brick masonry should have a per­
fect match. Twenty percent of a brick wall
area built with the standard modular brick
size is covered by mortar joints. The color of
the mortar joints has a substantial influ­
ence on the appearance of the brick color.
Mortar for a brick replacement or a
repointing of the mortar joints should be
weaker or equal to the existing mortar. The
mortar shall have a proportion specification
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for the mortar not stronger than the type
“N” (Brick Institute of America [BIA] M1-88
Specs) as follows:
Portland cement
1 part
Hydrated lime, type “S”
1 part
Sand
6 parts
The mortar mix should have no addi­
tives. Masonry cement should not be
allowed for the mortar mix.
Contractors often use waterproofing
additives in the mortar mix for repointing.
This can limit the breathing ability of the
mortar joints and could trap moisture
inside. Later, freeze and thaw cycles can
deteriorate the moisture-saturated mortar
joints. Therefore, waterproofing additives
are not recommended for mortar mixes
used for the repointing of brick masonry
walls. A good reference publication on
restoration and mortar joint repointing of
brick masonry walls is the BIA Technical
Note on Brick Construction #7F.
The use of salvage brick is not recom­
mended for brick replacement at the exteri­
or walls. When the brick masonry was
originally installed, a bond was developed
between the brick units and the mortar
joints. The brick unit initially was installed
over the bed of mortar and absorbed the
mortar’s moisture and cementitious parti­
cles within the first 45 to 60 seconds after
an installation. The cementitious roots filled
the pores of the brick unit, and an original
extend of bond was developed, which pro­
vided weather resistance for the brick
masonry wall. The old brick masonry could
have a very good bond between brick units
and mortar joints.
Contractors can clean the brick sur­
faces that were in contact with mortar
joints, but it may be next to impossible to
remove cementitious particles from the
brick unit pores. The pores of salvaged
brick units are partially or completely filled
with the original mortar cementitious parti­
cles, and if the salvaged brick is installed
into the new masonry wall, there will be no
more room in the pores of the salvaged
brick units to absorb the new mortar’s
cementitious particles. Thus, the bond
between the salvaged brick unit and the
new mortar joint will not be completely
developed, and the new masonry wall will
leak through the joints between the brick
units and the mortar joints.
Most authorities on masonry construc­
tion agree that water penetration through
masonry walls results from the incomplete­
ly filled mortar joints and incomplete bond
between brick and mortar. That is, water
penetrates through flaws at joints rather
than directly through the brick and mortar.
Thus, masonry walls of salvaged brick, with
their inferior mortar bond, are likely more
susceptible to water penetration and weak­
er under lateral loading than similar ma­
sonry of walls constructed of new brick
units. The salvage brick could be used for
interior walls or for the walls protected from
weather without any problems.
Old brick masonry walls should be eval­
uated from the structural engineering point
of view. Walls can be load bearing or can
carry their own weight only. If roof rafters or
floor joists are resting on a brick wall, it is a
load-bearing wall, and a structural engineer
should evaluate the wall conditions.
Solid masonry walls have an exterior
wythe called brick veneer that normally is
constructed from the face brick. The inner
wythes of a wall are called the backup. The
backup part of the wall is constructed from
brick or terra-cotta units. More recently,
cinder block or concrete block walls have
been used for the backup part of the
masonry wall. The brick veneer is anchored
to the backup wall system with brick head­
ers. A common wall has five or six courses
of stretchers built with a running bond pat­
tern and one course of headers embedded
into the wall backup system. The Flemish
bond pattern also has been used for the
brick veneer, consisting of alternating
stretchers and headers. Invisible diagonal
headers are used to anchor the brick veneer
with the running bond pattern only.
For replacement of brick veneer today, it
is not economical to use real brick header
courses. Thus, the stainless steel masonry
ties like “Helifix” can be used to anchor the
replaced brick veneer to the existing wall
backup system.
Vertical, diagonal, and horizontal cracks
in brick walls should be properly evaluated.
Figure 1: Tuck-pointing mortar joints. (Courtesy Brick Industry Association, Tech Note 7-F.)
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IN T E R F A C E
•
Table 1: Possible effects and sources of moisture penetrations.
(Courtesy Brick Industry Association, Tech Note 7-F.)
The vertical or horizontal displacement in
the crack could give a clue to where the
crack originated. Expansion cracks are
actually natural expansion joints and
should be treated as expansion joints.
Brick masonry normally has moisture
expansion and thermal expansion/contrac­
tion. This expansion and contraction is
absorbed by the brick veneer expansion
joints. Along the perimeter of the building,
the horizontal bend of the brick veneer
located above the top floor windows nor­
mally will experience moisture and thermal
movement. The brick veneer could expand
from the middle of the elevation towards
corners and could cause cracks at the
building corners. The moisture expansion of
a 50' brick veneer wall could be calculated
with the Brick Institute of America (BIA) fol­
lowing the formula: 0.0005 x L = 0.0005 x
50' x 12" = 0.30" or approximately 1/4".
The moisture expansion behavior of the
clay brick depends primarily on the raw
materials and the brick manufacturer’s fir­
ing temperatures. The moisture expansion
of the clay brick is an irreversible process
and most expansion takes place during the
first few years. However, the expansion will
continue at a much lower rate for the
remaining life of the building. The original
brick veneer had moisture expansion with­
in the first few years after completion. When
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the walls are repaired, the new brick veneer
will start to have moisture expansion.
Vertical and horizontal expansion joints
should be provided between the replaced
part of the brick veneer and the remaining
brick veneer at the exterior walls. Thus, the
replaced part of the brick veneer will be able
to move independently from the original
brick veneer and limit the number of new
cracks.
Many buildings were erected at the turn
of the 20th century in the U.S. with nonload-bearing, solid brick masonry walls.
Due to age, the solid masonry walls had a
tendency to absorb a substantial amount of
rainwater. Because of gravity and capillary
action, this moisture could migrate down
within the brick masonry wall, and be accu-
mulated at the top of steel spandrel beams.
Spandrel beam flashing could deteriorate,
causing rusting of the steel spandrel beam
and cracking of the solid masonry wall sup­
ported by this spandrel beam. Additional
rainwater could enter the wall system
through new cracks and could enter the
interior of the building, causing water stain­
ing and interior damages.
The author’s company developed a new
drainage system that could be installed at
the top of spandrel beams protecting the
steel beams from rusting and eliminating
water penetration into the building interior
space. This system was installed and suc­
cessfully tested at a number of projects. The
cost of this system installation is approxi­
mately $100 per linear ft. of the wall.
Cleaning of the old brick masonry walls
is a very complicated process. A power wash
with clean water could destroy the mortar
joints or a sand finish at the brick faces.
The water pressure at the wall surface
should be limited to 400 psi. A chemical
solution should be applied over the com­
pletely saturated (with clean water), brick
masonry wall. Thus, the chemicals will
work at the brick surface only and after
rinsing with clean water, chemicals will be
removed from the wall surface. The best ref­
erence publication on the cleaning of brick
masonry walls is the BIA Technical Note on
Brick Construction #20. For information
from the Brick Institute of America, phone
703-620-0010.
This paper was originally presented at
RCI’s 17th International Convention &
Trade Show in May 2002 in Galveston,
Texas.
Michael Gurevich
Michael Gurevich’s professional career spans 35 years and
two continents. He earned structural engineering degrees in
Minsk before emigrating from the U.S.S.R. in 1980. After­
wards, Gurevich worked in New York City for structural engi­
neering and architectural firms. Since 1985, he has been
involved with exterior masonry wall problems only. During
the last 18 years, Gurevich has presented brick masonry
technical seminars to over 1,400 groups, and is now associ­
ated with the New York City Brickwork Design Center of the
Brick Industry Association (BIA). For further information on
these seminars, call 212-684-4229.
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